Discovery eyes how brain sorts unwanted sounds

Paul Mayne // Western NewsSchulich School of Medicine & Dentistry professor Susanne Schmid is looking into the brain’s ability to filter out unwanted sounds and how this could eventually help in the treatment of schizophrenia and autism spectrum disorders.

A door slamming. Construction outside your window. The hum of an overhead light fixture. Our brain is constantly inundated with an overabundance of sensory information, requiring it to sort out unwanted sounds in order to focus on the task at hand.

While the sounds are not going anywhere, our ability to filter them – or what is called ‘acoustic habituation’ – has led one Western researcher to identify the underlying molecular mechanism that controls this capability.

Schulich School of Medicine & Dentistry professor Susanne Schmid said her research opens the door to potential new treatments, especially for people who experience disruptions in sensory processing, such as those with schizophrenia. Disruption in sensory processing was also recently added as a diagnostic marker for individuals with an autism spectrum disorder.

“Acoustic habituation is the most basic form of learning. But it is implicit; you don’t have to be conscious of it to learn it. Our brain is able to decide what’s not important and tune it out,” said Schmid, whose research was recently published in The Journal of Neuroscience. “This is important when we see those who aren’t able to habituate well. For them, the noises others can ignore would be very annoying to them. It becomes very disruptive.”

Using electrophysiology and pharmacological tools, Schmid has shown a potassium channel – specifically the BK channel – in the central nervous system can be regulated with drugs to increase or decrease these audio disruptions in animal models.

“By doing this, we are better able to understand what’s going wrong in people who do not habituate,” she said, adding it also means perhaps improving habituation in some individuals by targeting this mechanism and improving their sensory filtering.

By stimulating the neurons that convey the auditory information in the brain, Schmid explores the way they connect. In doing so, she found as someone habituates, the connection gets weaker, making the transmission signal less efficient. It hyperpolarizes the sounds and makes it more negative – in essence, turning down the sound. This lasts for about 10-15 minutes before reversing itself, Schmid explained.

While drugs exist to block these channels, not allowing habituation, Schmid said there are also drugs that can make these channels more excitable and thus increase habituation.

“This is something that, potentially down the road, could become a pharmaceutical target to increase habituation in individuals that have a deficit in that area, thereby increasing their ability to function and deal within their environment,” she said. “What we can do is help them to cope with that sensory information.”

Schmid added enhancing habituation and sensory filtering in those with autism spectrum disorder or schizophrenia might have beneficial effects not only on hyper- and hypo-sensitivity, but also cognitive function.